Interrupter circuit



June 1941- o. o. CROFFORD ,058

INTERRUPTBR CIRCUIT Filed Oct. 31; 1939 INVENTOR z. 0. Croffomi ATTORNEY M. June' 3, 1941- 2,244, v8

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" closure of the lower contact of relay W: will complete a circuit whichwill shunt the resistor R: out of the system.

The bridge will remain unbalanced as long as the lamps L1 and In haveimpedances which are substantially lower than the lmpedances oi theDuring, the unbalanced condition of the bridge, the relayW: will remainI operated.

However, the shunting of the resistor R3 out of the circuit will causean increased current to flow from the battery 81 through the variousarms of the bridge. The increased current will gradually increase thetemperature of the lamps L1 and In and hence their impedances will riseby corresponding amounts. After the impedances of the lamps L1 and Inhave been raised to values approximating the resistances of elements R1and R2, the bridge will become halanced and practically no current willthen iiow through the winding of the relay W2. Upon the release of therelayWz, the lamp L1 will become extinguished, and at the same time theshunt around resistor R: willbe removed.

The re-connection of the resistor R: to the circuit will then reduce theiiow oi current from the battery B1 through the various arms of thebridge. This will be accompanied by a reduction in the impedances of thelamps L1 and In as the temperatures of their filaments are lowered. Thebridge will then become unbalanced and the relay We will, therefore, bere-operated. The lamp In will become re-illuminated, and again theresistor R3 will be shunted out of the circuit. This action will berepeated again and again as long as the relay W1 remains operated.

Thus the relay W1, which may be, for example, the control relay of aringing circuit used in a telephone system, may be employed to initiatethe operation of the circuit illustrated in the drawing. The operationof the relay W1 will cause the lamp L3 to flash automatically at regularand predetermined intervals. These flashes will cease upon the releaseof relay W1.

Upon the operation of relay W1, the flow of current from battery B1 tothe winding of relay W: through the bridge will rise almost immediatelyto its maximum value. The time required to reach the maximum will bedetermined only by the inductance of the winding of relay W1. Thiscurrent is of course due to the unbalance of the bridge. ,As the lampsL1 and L: thereafter heat up, the bridge will approach a balancedcondition and the flow of current through the winding of relay W: willbe progreswell as by the currents required to operate and release therelay W2. The resistor Ra. which is connected into the circuit upon therelease or the relay W2, controls the rate at which the lamps L1 and L:will reach a predetermined high temperature. All of these factors may,oi. course, be adjusted as conditions may require.

The resistor R1 may be any stable resistance. If desired, it may be anadjustable resistance the magnitude 0! which is controlled according tothe operation or release of relay W2. The insertion of the resistor R3into the circuit in effect reduces the eilfective potential applied tothe bridge. Moreover, the resistor R: may be replaced by a non-inductivewinding mounted on the core of the relay W2. The signal lamp 1o may bereplaced by any other indicating device as will be apparent to thoseskilled in the art.

In one installation, the lamps L1 and Le were of the tungsten filamenttype and exhibited an impedance of 15 ohms when at room temperature, andapproximately 150 ohms when hot. Each of the resistors R1 and R: were ofapproximately 150 ohms. The battery B1 was a l0-volt battery. Thesevalues are given herein merely for illustrative purposes and are not tobe construed as limitations on the invention.

It will be understood that the lamps L1 and L: as well as the resistorsR1 and R: may, if desired, be enclosed within a single envelope in anywell known manner. These elements may be varied in practice to introduceany desired amount of delay between the successive flashes of the lampL2. By adjusting these elements to different predetermined magnitudes,the periodicity of the pulsating current produced may be changed to anypredetermined value.

In accordance with this invention, the lamps L1 and L2 may themselves bethe flashing lamps of the circuit. These lamps will flash in step withlamp L3. In such an arrangement the lamp La may be eliminated if sodesired.

It lamp L3 is thus eliminated and lamps L1 and In are used as the visualindicators, it will be necessary to adjust the elements of the circuitso that the flow of current through the lamps L1 and L: when relay W: isunoperated will be too small to illuminate these lamps. Upon theoperation of relay W2, however, the flow of current through lamps L1 andL2 will be suiiicient to adequately illuminate them. In this arrangementthe impedance oi the lamps will be varied over a wide range and thereliability of the circuit will therefore be improved. This arrangementwill be especially suitable if the lamps L1 and L2 and resistors R1 andR: are built into a single unit.

While this invention has been shown and described in certain particulararrangements merely for the purpose or illustration, it will beunderstood that the general principles of this invention may be appliedto other and widely varied organizations without departing from thespirit of the invention and the scope of the appended claims.

What is claimed is:

1. An interrupter comprising a Wheatstone bridge arrangement, two 0! theopposite arms of I the bridge including equal non-linear resistorsrespectively, the other two opposite arms of the bridge including twostable equal resistors, respectively, a source of voltage connected toone of thediagonals of the bridge, a relay the winding of which isconnected to the other diagonal or the bridge, and means responsive tothe operation of said relay for varying the tlow oi current from saidsource of voltage.

2. An electrical interrupter comprising tour elements arranged a arms01' a Wheatstone bridge, two oi the opposite arms of said bridgeincluding equal invariable impedancu, respectively, the other twoopposite arms of said bridge including two equal impedances which varywith the ilow oi current therethrough respectively. a source 01'potential connected as a diagonal of said bridge, a translating deviceconnected as the other diagonal of said bridge. and means responsive tothe iiow of current through said translating device to vary theeiiective potential of said source.

3. The combination oi two equal stable resistors, two equal non-linearresistors, said iour resistors being arranged as the arms of aWheatstone bridge, the opposite arms of which are said-two equal stableresistors, a source oi voltageia fli'th resistor connected in serieswith said source of voltage as one 01 the diagonals oi the bridge, arelay the winding which is connected asthe other diagonal oi the bridge,and means responsive to the operation of said relay for shunting thefifth resistor out of the circuit.

4.-A Wheatstone bridge interrupter circuit comprising two equal tungstenfilament lamps which are arranged as oposite arms of the bridge, and twoequal stable resistors arranged as the other two opposite arms of thebridge, a relay having its winding arranged as one 01' the diagonals oithe bridge, a source or potential, a variable resistor which isconnected along with said source as the other diagonal oi the bridge,and means responsive to the operation 01 the relay for changing themagnitude oi said-variable resistor.

5. An automatic current interrupter comprising two equal non-linearresistors. two equal stable resistors, said four resistors beingarranged as the arms of a Wheatstone bridge, a mm resistor connected toone of the bridge diagonals (or controlling the supply oi current to thebridge, a relay the winding of which is coupled to the other 01' thediagonals of the bridge, said relay being operated when the bridge isunbalanced and released when the bridge is balanced, and meansresponsive to the operation oi said relay for changing the magnitude 01'said fli'th resistor. I

6. A circuit interrupter comprising the combination of a translatingdevice such as a relay which may be operated and released, a source oipotential, a Wheatstone bridge interconnecting said source and saidtranslating device. said Wheatstone bridge having both linear elementsand non-linear elements as its arms, said translating device beingoperated when the bridge is unbalanced and released when the bridge isbalanced, and means responsive'to the operation of said translatingdevice to increase the effective potential oi said source so as toincrease the .iiow or current through said linear elements and saidnon-linearelements and to balance the bridge.

DANIEL OSMUND CROFFORD.

